Gemstone cuts, in particular for diamonds, are styles, patterns, templates, or designs used to cut and shape gemstones. A cut may take into account symmetry, proportioning, sizing, shape, and polishing of a gemstone. The type and style of the cut is a significant factor that influences a diamond's or other gemstone's light reflectivity and as a result, the brilliance or luminescence. The overall appearance of a gemstone or diamond can be enhanced by cutting the gemstone or diamond into different shapes and polishing the surface of the gemstone or diamond.
Based upon the shape and size of a diamond or other gemstone, a particular cut may be chosen that will determine the placement of various symmetrical facets. Placement of the facets and other cut shapes around the outer surface of the gemstone will ultimately influence the amount of light that will be reflected from the interior and exterior of the gemstone.
Most gemstones and in particular, diamonds, are unremarkable when initially recovered during the mining process. The gemstones may contain other types of natural deposits and may have an opaque or dull appearance. The subsequent cutting and polishing of the gemstone can radically transform its appearance and improve light reflectivity. By modifying the shape, light entering the gemstone can be redirected to maximize where the light exits the gemstone. This redirection of light enhances the sparkle or brilliance of a gemstone.
Stone cutters consider various factors when designing a particular cut. One consideration is the refractive index (“RI”) of a diamond or gemstone and another is the dispersive power of the diamond or gemstone. RI of a diamond or other gemstone is typically measured by sodium light and influences the brilliance of the gemstone. Brilliance is the amount of light reflected from the gemstone or diamond to the viewer. The dispersive power is the ability of the gemstone or diamond to separate light into individual spectral components. This is known as fire.
Once a gemstone is cut, the facets may form the exterior surface of the stone. The facets may also form the shape, design, or figure on the gemstone. Many diamonds will have a top crown section, a middle girdle section, and a lower pavilion section. The crown may include a top or table and a culet can be included at the nadir of the pavilion. Each section may be subdivided into other sections and cut as desired, forming a plurality of facets, shapes, and patterns. There are numerous popular gemstone cuts, including, for example, the “round brilliant” and the “passion cut.” Gemstones with a rectangular or square shape can be cut to include a “step-cut.” The step-cut includes facets that are rectilinear and arranged in parallel to the girdle in the horizontal plane. The corners can be truncated creating an octagonal outline, for example, in the “emerald cut.” As described by these representative examples, numerous gemstone cuts are known in the art, including many cuts that provide relatively high brilliance, RI, and/or fire to a viewer.